Electrode



July 15, 1930- w. c. GEER 1,770,514

ELECTRO-DE Filed April 8, 1925 ...NMF/HUH stares amsn- I @trice WILLIAM C. G3i-1ER, 0F AKRON, OHIO, ASSIGNOR TO THE B. F. GOODRICH COMPANY, OF

' NEW YORK, N. Y., A CORPORATION OF NEW YORK ErEcTRoian Application led April# 8, 1925. Serial No. 21,532.

This invention relates to electrodes of the character employed for the preparation of chemically pure metal cathod'es, of the character which serve as nucleus or initial plates 5 in the electrolytic deposition of metals, and has for an object to provide an electrode on which a nucleus plate of requisite size may be electrolytically deposited and readily removed. It is the customary practice in the electrolytic purilica-tion of copper to employ a relatively thin plate of electrolytically deposited copper as an initial cathode or nucleus plate upon which the purified copper is deposited v to buildup an in'got of commercial size. Heretofore, the initial cathode has' been formed on a large, heavy, oil-coated',copper electrode, called a stripping plate, from which it is removedby pulling oft1 the thin' I deposited copper plate.

There are certain difclilties'finherent in this mode of-operation. The copper deposits around the edges of the electrode make it necessary to cut` off the edges to open up a line of cleavagebetween the electrode and the deposited plate, giving a certain amount of copper scrap vwhichv must be reworked, and, due to the cohesion of copper to copper, the stripping operationis accompanied by'a considerable loss in defective plates. v

In the present invention'these diliiculties are overcome to a large degree by the employment of a plate electrode made of a vulcanized-rubber composition containing a sufiicient amount of a conducting material,

such as graphite, and provided with .a non-` conducting hard-rubber border. The copper when precipitatedvfrom solution by an electric current will thus be deposited only over the central or graphite-'containing portion of the electrode and the newly formed copper plate of electrolytic metal may be readily stripped therefrom. v

the `accompanying drawings, Fig.- 1 isa perspective view of an electrode embodying cmy invention; Fig. 2 is a section onrline 2f-2 of'Fig.. 1'; and Fig. 3 is a perspective view' b of a modified form Cif-electrode, parts being broken' away to show the;A inserted copper plate."- f

Referring to the drawings, I show in Figs. 1 and 2 an electrode consisting of abody portion 10 of an electrically-conducting vulcanized rubber having an upstanding lug 11 at one side, and a border portion 12 of nonconducting hard rubber. As shown, the border 12 does not extend across the end of the lug 11 since this portion of the electrode is in use always above the levelof the electrolyte. The lug 11 is provided with a 'metal bushing 13 for the connection of an electric current supply wire thereto'.

In making the electrode, a conducting rubber composition suitable for the body-portion is prepared, and then shaped to the form desired, preferably Vthe rectangular' form4 shown in the drawing. The border strips, out or extruded from a suitable hard-rubber composition, ar'e then placed aboutA the b ody portion, and the whole is cured, preferably in a mold of proper size, under heat and pressure to form an electrode in which the 'body and the border are coalesced into a truly integral structure. I have found that a composition consisting of rubber, 100 parts by weight, sulfur 33 parts, graphite 150 parts, organic accelerator 1 part, conducts electric i ity with a fair degree of efficiency, receives deposition of copper uniformly -in s'uch manner as to form satisfactory sheets 'or plates,-

the substitution of slate-flour for the graphite of the above recipe produces a' satisfactory non-conducting compound.

In the modification illustrated in 3,

the body portion of the electrode is formed of a central copper plate 15 'either-side of which is covered with a layer 16 of anelectricallyconducting rubber compound, the copper insert servingto secure a better distribution of current throughout the exposed surfaces of thev body-portion. The border 12 -is constructe'd andthe whole electrode is assembled and cured in amanner'similar to that above set forth. g

In using either of the electrodes lierein described for forming a cathode sheet or nucleus plate for use in electrolytic purification of copper, the electrode is immersed in a suitable electroplating solution, such as a strong aqueous solution of potassim cyanide and blue vitriol, and the lug 11 connected with the negative conductor of an electric circuit. A copper plate, connected With the positive conductor of an electric circuit, is also suspended in the electroplating solution. The flow of current through the solution effects a deposition of copper only on the graphite surfaces of the electrode, leaving the non-conducting border portion free of deposited copper. Vhen a suitable thickness of copper has been deposited on the electrode, usually about 11B- inch, the electrode is taken from the solution, Washed, and the sheet of copper stripped therefrom. The stripping operation is readily performed since the deposited sheet is confined to the area of the graphite body portion, to Which-the copper does not firmly adhere, thus giving Well defined edges to the sheet at the unction of the border with the body portion of the electrode.

WVhile I have specified herein the use of graphite in an electricallyconducting rubber composition. it is to be understood that'other coniminuted electrical conductors may be einployed in lieu thereof. Thus, comminuted copper may be used Where a copper cathode is to be formed, or zinc dust, Where it is desired to form a zinc cathode. I therefore do not wholly limit my claims to the specific rubber surrounding said body portion and formed integrally therewith.

2. A plate electrode comprising a body portion consisting of a sheet of copper covered on both. sides with a hard rubber compound containing a high percent of graphite, and a border of non-conducting hard rubber surrounding said body portion, the Whole being united into an integral plate by vulcanization.

3. A plate electrode comprising a metal core covered at least in part with an electricallyconductive rubber composition.

4. A plate electrode comprising a sheet of metal covered on bot-h faces with an electrically-conduetive rubber composition. v

5. A plate electrode including a body portion comprising a sheet of metal covered at least'as to one face with an electrically-conductive rubber composition, and a border of non-conductive material united integrallythereto.

6. A plate electrode including a body portion comprising a sheet of metal covered on both sides with an electrically-conductive rub- 

